This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-276360, filed Sep. 29, 1999; No. 11-292730, filed Oct. 14, 1999; No. 11-305533, filed Oct. 27, 1999; No. 11-312399, filed Nov. 2, 1999; and No. 11-357400, filed Dec. 16, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a method and an apparatus for automatically soldering a lead wire to a solar battery to connect the lead wire to positive and negative electrodes of a photovoltaic module for directly converting solar energy to electrical energy and deriving an output from the photovoltaic module.
A photovoltaic module for directly converting solar energy to electrical energy has a layered body, in which a transparent electrode layer, a photovoltaic semiconductor layer and a rear surface electrode layer are laminated in this order on an insulating substrate, such as a glass substrate. The layered body is divided into a plurality of photoelectric converting cells by a laser scriber or the like. The photovoltaic cells are electrically connected to one another in series or parallel.
As disclosed in, for example, Jpn. Pat. Appln. KOKAI Publications Nos. 9-326497, 9-135035 and 9-83001, a photovoltaic module has lead wire soldering regions at both end portions.
In the lead wire soldering regions, a number of solder bumps serving as positive and negative electrodes are formed in a row at regular intervals. Lead wires are connected to the solder bumps, so that an output of the photovoltaic module can be derived. The lead wires are connected to a terminal box attached to the rear surface of the photovoltaic module.
Further, for example, Published Japanese Patent No. 2691685 and Jpn. Pat. Appln. KOKAI Publication No. 9-295133 disclose an apparatus for forming solder bumps in lead wire soldering regions of a photovoltaic module. With the apparatus, bumps are soldered efficiently and securely by applying ultrasonic vibration to a soldering iron.
In the lead wire soldering regions of the photovoltaic module, solder bumps having a spot diameter of about 2 mm are formed in a row at intervals of about 20 mm and soldered by means of ultrasonic soldering. Thereafter, lead wires made of solder-plated copper foil or the like are placed along the row of the solder bumps. The lead wires are pressed on the solder bumps by a soldering iron, while the lead wires are heated from above. Thus, the lead wires are soldered to the solder bumps.
Conventionally, when lead wires are connected to the lead wire soldering regions on both sides of the photovoltaic module, first, solder bumps are formed as preliminary solder in the lead soldering regions, thereafter lead wires made of solder-plated copper foil or the like are placed along the row of the solder bumps, and the lead wires are soldered to the solder bumps. These process are performed by manual works.
Therefore, when the lead wires are arranged along the row of the solder bumps and the soldering iron is pressed against the lead wires from above, the lead wires may be shifted or wrinkled. To solve this problem, weights are hung from the ends of the lead wires, so that tension is applied to the lead wires by the gravity of the weights during the soldering process.
However, the manual work of soldering lead wires to solder bumps is inefficient, requires a number of steps for mass production, and increases costs. In addition, since the lead wires are soldered with tension applied to the lead wires by the weights, the lead wires soldered between solder bumps are strained. Under these conditions, if the photovoltaic module is mounted on the roof of a building or the like, the lead wires may be contract when it is cooled, resulting in damage or removal from the solder bumps.
Further, the lead wires are connected to the lead wire soldering regions on both sides of the photovoltaic module in the two steps of: forming preliminary solder bumps in the lead wire soldering regions; and placing the lead wires made of solder-plated copper foil or the like along the row of the solder bumps and soldering the lead wires to the solder bumps. Therefore, attachment of the lead wires is complicated and inefficient.
In the case of a large-size photovoltaic module, the insulating substrate has a size of 910 mmxc3x97455 mm, and solar battery sub-modules are formed on the substantially overall surface of the insulating substrate. In the case of a small-size photovoltaic module which is mounted on roofing tiles, likewise, a transparent electrode layer, a photovoltaic semiconductor layer and a rear surface electrode layer are laminated in this order on an insulating substrate of the required small size. The layered body is divided into a plurality of photoelectric converting cells by a laser scriber or the like. The photoelectric converting cells are electrically connected to one another in series or parallel.
A photovoltaic module may be produced as follows: a plurality of solar battery sub-modules are formed with dividing regions interposed therebetween on an insulating substrate; and thereafter the insulating substrate is cut at the dividing regions, so that a plurality of photovoltaic modules can be formed.
Then, belt-shaped lead wires made of solder-plated copper foil or the like are soldered to positive and negative electrodes of each solar battery sub-module. The ends of the lead wires are connected to the terminal box attached to the rear surface of the photovoltaic module in order to derive an output.
Conventionally, in the case of a small-size solar battery, solar battery sub-modules are formed on an insulating substrate of that size in the same manner as in the case of a normal size substrate. When producing so-called multiple photovoltaic modules after forming a plurality of solar battery sub-modules on the insulating substrate, the insulating substrate is cut at the dividing regions to form a plurality of photovoltaic modules and the lead wires are connected to the lead wire soldering regions on both sides of each photovoltaic module. In other words, the solder bumps are first formed by means of a bump soldering iron in the lead wire soldering regions on both sides of the divided photovoltaic module, and thereafter the lead wires are soldered to the solder bumps by means of a lead wire soldering iron.
As described above, when a layered body is formed on a small-size insulating substrate or scribed by a laser, it is troublesome to frequently convey the substrate or a film forming apparatus and a laser scriber. Moreover, an additional jig or carrier, or an additional work, such as changing of the work pattern for laser processing, is required to fix or convey the insulating substrate to the film forming apparatus or the laser scriber. For this reason, the forming or laser-scribing of a layered body is inefficient and costly. Furthermore, when the lead wires are soldered to the lead wire soldering regions on both end portions of the small-size photovoltaic module, it is troublesome to convey the battery module to or from a mount table, whether the soldering is carried out by hands or an automatic soldering apparatus. Further, since the soldering cannot be carried out continuously, the work is insufficient, resulting in an increase in costs.
To guide an output from the photovoltaic module to the terminal box mounted on the rear surface of the module, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-326497, lead wires connected to the terminal box are soldered to positive and negative electrodes formed on both ends of the photovoltaic module. The soldering is carried out in the state where an electrode is brought close to or overlap an end portion of the lead wire, so that the solder is deposited across the electrode and the lead wire. Likewise, according to the conventional art, when the direction of a wire is to be changed in the middle of a conducting path from the electrode to the terminal box, first and second lead wires are individually prepared, the end portions of the lead wires are caused to intersect at right angles, and solder is deposited at the intersection. Thus, the direction of the conducting path is changed.
However, according to the aforementioned conventional structure, the electrode and the lead wire to be soldered are merely brought close to or overlap each other, and are not bounded to each other. Therefore, when they are soldered, the relative position therebetween is liable to be deviated and. Since they must be soldered taking account of this matter, the soldering workability is low. In addition, the reliability of the soldering interconnection may be lowered due to the positional deviation. Under the circumstances, it is desired to increase the workability and the reliability of the soldering in order to improve the quality of the photovoltaic modules.
An object of the present invention is to provide a method and an apparatus for soldering a lead wire to a solar battery, which can automatically connect lead wires to a row of solder bumps formed in a lead wire soldering region of a solar battery, so that the working efficiency can be improved.
According to the present invention, a lead wire is fed out from a lead wire feeding section located at an end portion of a row of solder bumps, and laid over all length of the row. Thereafter, the lead wire is held on the solder bump, while the lead wire is welded to the solder bump, beginning with the top end of the lead wire. The above operation and an operation of releasing the lead wire are repeated. Then, the lead wire, from the top end toward the rear end, is successively soldered to the solder bumps. Thus, the lead wire can be soldered to the solder bumps at high speed, thereby improving the working efficiency. In addition, the tension of the lead wire is kept substantially constant, while the lead wire is soldered to the solder bumps. Therefore, the lead wire is prevented from being wrinkled or cut, resulting in the advantage that an even thin and brittle lead wire can be soldered reliably.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.